Pushing the boundaries with research and innovation in forest engineering October 9-13, 2011, Graz 1 Residual stand damage following ground-based skidding operation (Case study: Kheyrud Forest) Meghdad Jourgholami, Baris Majnounian Department of Forestry and Forest Economics Faculty of Natural Resources University of Tehran Zob-e-Ahan street, 3158777878 Karaj, Iran mjgholami@ut.ac.ir Abstract: Hyrcanian (Caspian) Forest in northern Iran has a richness of biological diversity, with endemic and endangered species. The use of ground-based skidding is well accepted practice for the extraction of timber from the forest, but this has tended to cause the greatest environmental problems. The aim of the study was to evaluate and comparison of environmental impacts, residual stand damage, regeneration, and to quantify these effects such as: extent of the damage, wounding patterns, size and distribution after logging operations that utilized two different methods: short-log and long-log. A Timberjack cable skidder was used and the study location was in the Kheyrud Forest. Post harvesting assessment of damage to the residual stand was compared along skid trail by 100% inventory method and also for the assessment of regeneration damage along winching strips. The results showed that along winching strips the percentage of damage to the regeneration was 44 and 36 %, while the tree damages along skid trails reached 2.3 and 4.1 % in the short- and long-log methods, respectively. The greatest average amount of damage to a bole occurred along the first 1 m up from the ground (97%) and also within 4 m of the skidder centerline (80%). These results clearly show that the short-log method causes less damage to the residual stand than the long-log method. Tree location to skidder trail appears to have a significant effect on the number and height of scars on a tree. Well designed and constructed trails should be wide enough to allow wood extraction from the forest. Damage to the residual stand might be reduced by proper planning and training of logging crews. Keywords: environmental impacts, forest harvesting method, residual stand damage, regeneration 1 Introduction Hyrcanian (Caspian) forest in northern Iran has a richness of biological diversity, with endemic and endangered species, and a diverse range of economic and social conditions. About 45% of the Hyrcanian forests are located in mountainous areas, where forest lands are not readily accessible with ground-based logging equipments, but cable yarding technologies are still undeveloped in this forest area. Accessibility is the most critical factor influencing feasibility of operations in mountainous terrain (Heinemann 2004). Rubber-tired skidders are used on the more gentle slopes and on designated skid roads in steeper terrain. Crawler tractors (bulldozers) are used on steeper topography to skid direct to the landing (Sobhani and Staurt 1991). The use of wheeled and tracked skidders is a widely seen and well accepted practice in Hyrcanian forests. It is also the one that tends to cause the greatest environmental problems. From the beginning of the twentieth century, the increasing use of mechanized wood harvesting brought with it the problem of damage to the remaining trees in forest stands (Vasiliauskas 2001). Not all tree species are equally susceptible to mechanical injury. Dameg to the residual stand in forest operations is most often caused during transport of timber (Vasiliauskas 1993; Han 1998; Froese and Han 2006; Kosir 2008). Trees are wounded by machines and logs under extraction (Siren 1982). Most of the resulting wounds occur at or near the base of a tree (Bettinger and Kellogg 1993; Kovbasa 1996; Han 1998; Froese and Han 2006). In spruce stands harvested by partial and shelterwood cuttings, only 15 per cent of all tree wounds were situated higher than 0.5 m, and over 60 per cent of the trees were damaged at the root collar,